DISTRIBUTION OF VOLCANIC ERUPTIONS IN KAMCHATKA BY MAGNITUDES DURING THE LAST 50,000 YEARS THE GEOLOGICAL EFFECT OF AN EXPLOSIVE VOLCANISM AND PREDICTIVE ESTIMATES

Abstract

In Kamchatka volcanism has occurred since the Cretaceous period. There are about 7100 volcanic structures with age from 2-2.5 million years to the present. There are 20 active and 14 potentially active polygenetic volcanoes, as well as 10 modern and Holocene fields of monogenic volcanism, zones of multi-edifice extrusive volcanism and calderas [1]. Over the past 1000 years, the linear heat power of eruptive volcanism in Kamchatka is estimated at about 10 MW per 1 km of its volcanic arc. This is 4–5 times more than in the Kuril Islands, in Japan or in New Zealand, and is only inferior to the linear power of Icelandic volcanism (15 MW) [2]. In historical times, about 10% of all volcanic eruptions in the world occurred in Kamchatka (for the range of volcanic explosivity index, VEI = 2–5). This is quite a lot because the length of the volcanic arc of Kamchatka is approximately 900 km, which accounts for only about 2% of the sum of the lengths of all volcanic arcs on Earth. This is due to the unprecedented high productivity of the giant volcanoes of the Northern group of Klyuchevskoy, Shiveluch and Ploskiy Tolbachik, each of which erupts from 20 to 60 million tons of volcanic products per year. The distribution of the volume of ejected pyroclastic (Vp) for eruptions of Kamchatka volcanoes in the last 50,000 years obeys a power law with the index – bdiff = –0.90 ± 0.14 (95%). Assuming a steady state volcanism [3], the average intervals (T) between future eruptions in Kamchatka are estimated as follows: once a year (VEI = 2), every 5 years (VEI = 3), every 40 years (VEI = 4), every 300 years (VEI = 5), every 3,300 years (VEI = 6) and every 22,000 years (VEI = 7). The total geological effect of Kamchatka volcanoes is estimated at about 50 km3 of pyroclastic over 1000 years (VEI = 2–7).